An eepSite is a website that is hosted anonymously - you can access it by
setting your web browser's HTTP proxy to use the I2P proxy (typically it listens
on localhost port 4444), and browsing to the site.

What is I2P?

I2P is a generic anonymous and secure peer to peer communication layer.
I2P exposes a simple layer that applications can use to anonymously and securely send messages to each other. The network itself is strictly message based (ala IP), but there is a library available to allow reliable streaming communication on top of it (ala TCP). All communication is end to end encrypted (in total there are four layers of encryption used when sending a message), and even the end points ("destinations") are cryptographic identifiers (essentially a pair of public keys).

Thus I2P is a
network that sits on top of another network (in this case, it sits on top of the
internet) and can deliver a message anonymously and securely
to another location. Visit the I2P Home Page
or click for a detailed
How To or in-depth
technical information.

"eep" is a common prefix for I2P services, for example: "eepSite" or "eepProxy". Research
suggests "End-to-End Protocol" or "Encrypted-Encrypted Peer". Apocryphal sources
suggests that "eep" is simply a phoneme for IIP (Invisible Internet Project) and has no inherent meaning.